Causes of blistering on PCB board surface

Blistering on the surface of a printed circuit board (PCB) is a common issue that can compromise the integrity and reliability of the board. Blistering refers to the formation of bubbles or raised areas on the PCB's surface, which can lead to electrical connectivity issues, reduced performance, and even failure of the electronic device. In this article, we will explore the various causes of blistering on PCB board surfaces and provide potential solutions to address this concern effectively.

1. Moisture Absorption

One of the primary causes of blistering on PCB board surfaces is moisture absorption during the manufacturing process. Moisture can be present in the PCB materials, including the core, prepreg, and copper foils. When exposed to high temperatures during soldering or assembly processes, the trapped moisture can vaporize, leading to blister formation on the surface. 

Solution: To mitigate the impact of moisture absorption, it is crucial to store PCB materials in a controlled environment with low humidity levels. Additionally, ensuring proper drying of the PCB materials before assembly can prevent moisture-related blistering.

2. Outgassing

Outgassing occurs when volatile compounds trapped within the PCB materials are released during high-temperature processes, such as soldering or reflow. The released gases can get trapped under the solder mask or conformal coating, leading to blister formation.

Solution: Using materials with low outgassing characteristics and conducting thorough material testing can help minimize the potential for outgassing. Adequate curing of solder masks and conformal coatings can also prevent gas entrapment.

3. Delamination

Delamination refers to the separation of different layers within the PCB, which can result from inadequate bonding during the manufacturing process. Delamination can lead to the formation of blisters on the PCB surface.

Solution: Proper handling and storage of PCB materials, as well as controlling the lamination process parameters, are crucial to prevent delamination. Regular inspection and testing during the manufacturing process can help identify and address delamination issues early on.

4. Entrapped Solvents

During the application of solder mask or conformal coating, solvents are often used as carriers for the coating materials. If the solvents become trapped within the coating layer or between the coating and the substrate, they can lead to blister formation during curing or thermal stress.

Solution: Employing suitable coating application techniques and ensuring proper ventilation during the curing process can help prevent the entrapment of solvents. Using low-VOC (volatile organic compound) coatings can also minimize solvent-related issues.

5. Thermal Stress

PCBs are exposed to thermal stress during various stages of their lifecycle, such as during soldering, reflow, or operation. Repeated thermal cycles can cause the expansion and contraction of different materials, leading to blistering on the PCB surface.

Solution: Careful selection of materials with compatible thermal coefficients of expansion (TCE) and proper thermal management can help reduce the impact of thermal stress on PCBs. Additionally, designing the PCB layout to evenly distribute heat and thermal dissipation can mitigate thermal stress-related blistering.

6. Manufacturing Defects

Blistering can also result from manufacturing defects, such as inadequate cleaning, contamination, or improper handling of PCB materials during production.

Solution: Implementing stringent quality control measures and conducting regular inspections during the manufacturing process can help identify and rectify potential manufacturing defects that may lead to blistering.

Conclusion：

Blistering on the surface of PCB boards can result from various factors, including moisture absorption, outgassing, delamination, entrapped solvents, thermal stress, and manufacturing defects. Addressing these issues requires a combination of proper material handling, suitable material selection, controlled manufacturing processes, and thorough quality control measures. By taking proactive steps to prevent blistering, PCB manufacturers can ensure the reliability, performance, and longevity of electronic devices that rely on these crucial components. Additionally, continuous research and development in PCB materials and manufacturing techniques will further enhance the resilience and durability of PCBs, contributing to the advancement of the electronics industry as a whole.